Are JDBC Driver connections limited by the number of CALs on the SQL Server ?

Answer

CAL stands for Client Access License.
As far as we know, Microsoft offers 2 different licensing schemes for SQL Server.
The first they refer to as "processor" licensing.
More can be read about it here:
http://www.microsoft.com/sql/howtobuy/processor.asp
The second they refer to as "CAL" licensing.
More can be read about it here:http://www.microsoft.com/sql/howtobuy/servercal.asp
We cannot speak for Microsoft's position on these various licensing choices, and we do not know in what way (if at all) they enforce CAL licensing.
That would be more a question for Microsoft.
We can say that if you have SQL Server on machine A, and you have your code that uses JTurbo on machine B then machine B is 1 client. So, if using the CAL licensing scheme you would need to purchase at least 1 CAL (for machine B). You could then use JTurbo on machine B to make any number of JDBC Connections to the SQL Server on machine A that you wish.